Today, let's measure the color of water. The
University of Houston's College of Engineering presents this series about the
machines that make our civilization run, and the people whose ingenuity created them.

The Color of Water is the title of a book by
Black author James McBride about his White mother. When asked which color God was,
she told him, He is the color of water. The metaphor is powerful; however,
water might have color after all.

But I'm ahead of my story. Let us back up and meet Walthère Victor Spring, born in
Belgium in 1848. Spring's father was a physiology professor at Liège, and young
Spring was a disappointment -- only a so-so scholar and especially weak in classical
languages. So he quit school and went off to become a gunsmith -- a trade for which
he had real talent.

As his confidence emerged, Spring retook the university entrance exams and passed them.
He got a degree in mining engineering, but grew more interested in science. He went
on to study physical chemistry with Friederich Kekulé and Rudolph Clausius.

Like his father, he became a professor at the University of Liège. What served him
there was not any mastery of classical languages, but his gunsmithing. He was a fine
experimentalist who took a great interest in the writings of British physicist
John Tyndall.

Tyndall, himself a great experimentalist and observer, wrote about how powdered snow
was compacted into glaciers. Spring responded with experiments in which he compressed
all sorts of granular materials in a specially designed screw press. Each turned into
an extraordinarily dense solid. Then he used those same techniques to study phase
equilibrium in solids.

He followed Tyndall's lead again in 1870. Tyndall had previously suggested that the sky
appears to be blue because short wavelength light -- blue light -- is scattered sideways.
Tyndall thought that particles in the air caused the scattering. Later, it turned out
that the air molecules themselves scatter blue light. Tyndall also did
a very clever experiment: he invented means for creating optically
pure air, with no particulates at all.

He did not see any color in air, but Spring said, Wait a minute. Maybe if I create
optically pure water, it will have a color of its own. He put his talent with apparatus
to the creation of an 85-foot-long tube filled with almost perfectly clean water. Then
he shone white light along it. It worked!

He was able to tell us that water is
"a pure cerulean blue similar to that of the sky at its zenith when seen from a high mountain."
Spring didn't try to explain that blue. But we now know that the long red wavelengths
in his light beam were absorbed by the water. Only the blue got through, making it seem blue.

And, the color of God? That too seems to depend on how the light we cast returns to us.
Others saw black or white, while McBride's mother saw no color at all. So, as for the
color of water, I need to go back to Crater Lake, Oregon
-- to contemplate its deep soul-settling blue while I think about measurement and perception.

I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.